Portable lap desks having a pillow-like portion of flexible material filled with a dry flowable material secured to a hard planar writing surface are well known in the art. These portable lap desks provide a light weight portable desk surface, which may be used almost anywhere, on almost any surface, which desk is durable and relatively inexpensive to manufacture. Examples of these portable lap desks and methods for their manufacture are described in U.S. Pat. No. 4,052,944 entitled "Portable Shuffle Desk."
It is well known in the art to manufacture portable lap desks by cementing a flexible pillow-like casing to the perimeter of a rigid sheet material known as the subplanar, which subplanar has a port through which a flowable granular material may be inserted into the flexible pillow-like casing. In particular, the method of the prior art provides that the flowable granular material is inserted into the flexible pillow-like casing by hand, which method is a time consuming and inefficient operation.
Generally, the subplanar member has door-like portions or elements to close the port through which the granular material is inserted. The rigid planar writing surface is attached to the pillow-like structure by the hand application of cement to the subplanar element and to the overlapping edges of the pillow-like portion to assure that the pillow is attached to the rigid planar member about its entire perimeter.
The method of the prior art suffers numerous disadvantages, such as the difficulties experienced in locating the subplanar member with respect to the flexible pillow casing to assure that the flowable granular material is easily inserted into the interior of the casing, while simultaneously assuring that a uniform and proper amount of excess fabric is available from the border of the pillow to permit the fabric to overlap the subplanar and be cemented to the exterior planar surface.
Further, the method of the prior art suffers the disadvantage of requiring a workman to load the pillow-like casing with a flowable granular material by hand, which operation is time consuming and inefficient as well as wasteful of the granular material. In particular, when the granular material is expanded polystyrene beads, the workman experiences great difficulty in placing the material within the pillow-like structure without excessive spillage and other losses of the material. Generally, shops which employ this hand loading method are subject to the persistent problem of excess granular material being present on the shop floors, requiring the additional labor expense of removing the waste granular material from the shop.
Further, the method of the prior art provides no means by which the peripheral pillow material may be easily retained on the surface of the subplanar elements while cement is applied to the fabric for attachment to the exterior planar surface.
Consequently, a need exists in the art for a means for easily locating the subplanar element relative to the pillow-like casing to allow easy insertion of the flowable granular material into the pillow, and for a means of placing the flowable granular material within the pillow casing in a quick and efficient manner without the risk of spilling any of the material. Further, a need exists in the art for retaining the fabric perimeter of the pillow-like casing on the surface of the subplanar element so that the fabric may overlap the subplanar element and allow efficient application of cement to ensure that the fabric is adequately secured to the surface of the rigid planar writing surface.